U.S. patent application number 12/969234 was filed with the patent office on 2011-06-23 for active mount, lithographic apparatus comprising such active mount and method for tuning such active mount.
This patent application is currently assigned to ASML NETHERLANDS B.V.. Invention is credited to Hans BUTLER, Pieter Johannes Gertrudis Meijers, Hendrikus Johannes Schellens.
Application Number | 20110149265 12/969234 |
Document ID | / |
Family ID | 43778552 |
Filed Date | 2011-06-23 |
United States Patent
Application |
20110149265 |
Kind Code |
A1 |
BUTLER; Hans ; et
al. |
June 23, 2011 |
ACTIVE MOUNT, LITHOGRAPHIC APPARATUS COMPRISING SUCH ACTIVE MOUNT
AND METHOD FOR TUNING SUCH ACTIVE MOUNT
Abstract
A lithographic apparatus includes an illumination system
configured to condition a radiation beam, a support constructed to
support a patterning device, the patterning device being capable of
imparting the radiation beam with a pattern in its cross-section to
form a patterned radiation beam, a substrate table constructed to
hold a substrate, and a projection system configured to project the
patterned radiation beam onto a target portion of the substrate.
The projection system is mounted on a reference structure of the
lithographic apparatus by a mount of the lithographic apparatus.
The mount includes a first piezoelectric element to exert a force
on the projection system, a second piezoelectric element to measure
the force, and an interconnection member interposed between the
first and second piezoelectric elements, the interconnection member
comprising a cut.
Inventors: |
BUTLER; Hans; (Best, NL)
; Meijers; Pieter Johannes Gertrudis; (Horst, NL)
; Schellens; Hendrikus Johannes; (Bergeijk, NL) |
Assignee: |
ASML NETHERLANDS B.V.
Veldhoven
NL
|
Family ID: |
43778552 |
Appl. No.: |
12/969234 |
Filed: |
December 15, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61288963 |
Dec 22, 2009 |
|
|
|
Current U.S.
Class: |
355/72 ;
310/338 |
Current CPC
Class: |
G03F 7/70833 20130101;
H01L 41/0825 20130101; G03F 7/70825 20130101; F16F 15/005
20130101 |
Class at
Publication: |
355/72 ;
310/338 |
International
Class: |
G03B 27/58 20060101
G03B027/58; H01L 41/04 20060101 H01L041/04 |
Claims
1. A mount to hold an object, the mount comprising: a first
piezoelectric element configured to exert a force on the object; a
second piezoelectric element configured to measure the force, and
an interconnection member interposed between the first and second
piezoelectric elements, the interconnection member comprising a
cut.
2. The mount of claim 1, wherein the cut is dimensioned to provide
for a desired cross talk between the first piezoelectric element
and the second piezoelectric element.
3. The mount of claim 2, wherein the desired cross talk is
substantially opposite to a cross talk between the first
piezoelectric element and the second piezoelectric element caused
by a parallel resilience of the active mount.
4. The mount of claim 1, wherein the cut comprises a lateral cut in
a plane substantially perpendicular to a direction of the
force.
5. The mount of claim 4, wherein lateral cuts are provided at
opposite sides of the interconnection member.
6. The mount of claim 5, wherein a depth of the cuts is dimensioned
so that a remaining part of the interconnection members between the
cuts has a width in a range from about 40% to 80% of a width of the
interconnection member.
7. The mount of claim 4, wherein the cut comprises a triangular
cut.
8. The mount of claim 7, wherein the cut is provided at opposite
sides of the interconnection member.
9. The mount of claim 7, wherein a depth of the cuts is dimensioned
so that a remaining part of the interconnection members between the
cuts has a width in a range from about 40% to 80% of a width of the
interconnection member.
10. The mount of claim 1, wherein the cut extends along a direction
of the force.
11. The mount of claim 10, wherein two cuts are provided in planes
substantially perpendicular to each other.
12. The mount of claim 11, wherein the cuts extend through the
first and second piezoelectric elements, thereby dividing the
interconnection member and the first and second piezoelectric
elements in 4 parts.
13. The mount of claim 11, wherein a plurality of parallel cuts are
provided along the planes, so as to form poles in a part of the
interconnection member.
14. The mount of claim 13, wherein, seen along the direction of the
force, double cuts are provided, the double cuts leaving an
interconnection plate between the poles.
15. The mount of claim 1, wherein a deformation member, such as a
piezoelectric actuator, is comprised in the interconnection member,
the deformation member configured to deform the interconnection
member.
16. The mount of claim 3, wherein an actuator is provided to change
a stiffness of the parallel resilience.
17. The mount of claim 16, wherein the actuator is a piezoelectric
actuator,
18. A lithographic apparatus comprising: an illumination system
configured to condition a radiation beam; a support constructed to
support a patterning device, the patterning device being capable of
imparting the radiation beam with a pattern in its cross-section to
form a patterned radiation beam; a substrate table constructed to
hold a substrate; a projection system configured to project the
patterned radiation beam onto a target portion of the substrate,
the projection system being mounted on a reference structure of the
lithographic apparatus by a mount of the lithographic apparatus,
the mount comprising a first piezoelectric element configured to
exert a force on the projection system, a second piezoelectric
element configured to measure the force, and an interconnection
member interposed between the first and second piezoelectric
elements, the interconnection member comprising a cut.
19. A method for tuning a mount, the mount to hold an object and
comprising a first piezoelectric element configured to exert a
force on the object, a second piezoelectric element configured to
measure the force, and an interconnection member interposed between
the first and second piezoelectric elements, the method comprising
repeating (a) measuring a remaining cross talk of the mount, and
(b) cutting into the interconnection member, until the remaining
crosstalk reaches a desired level.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority and benefit under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Patent Application No. 61/288,963,
entitled "Active Mount, Lithographic Apparatus Comprising Such
Active Mount and Method For Tuning Such Active Mount", filed on
Dec. 22, 2009. The content of that application is incorporated
herein in its entirety by reference.
FIELD
[0002] The present invention relates to an active mount, a
lithographic apparatus including such active mount and a method for
tuning such active mount.
BACKGROUND
[0003] A lithographic apparatus is a machine that applies a desired
pattern onto a substrate, usually onto a target portion of the
substrate. A lithographic apparatus can be used, for example, in
the manufacture of integrated circuits (ICs). In such a case, a
patterning device, which is alternatively referred to as a mask or
a reticle, may be used to generate a circuit pattern to be formed
on an individual layer of the IC. This pattern can be transferred
onto a target portion (e.g. including part of, one, or several
dies) on a substrate (e.g. a silicon wafer). Transfer of the
pattern is typically via imaging onto a layer of
radiation-sensitive material (resist) provided on the substrate. In
general, a single substrate will contain a network of adjacent
target portions that are successively patterned. Conventional
lithographic apparatus include so-called steppers, in which each
target portion is irradiated by exposing an entire pattern onto the
target portion at once, and so-called scanners, in which each
target portion is irradiated by scanning the pattern through a
radiation beam in a given direction (the "scanning"-direction)
while synchronously scanning the substrate parallel or
anti-parallel to this direction. It is also possible to transfer
the pattern from the patterning device to the substrate by
imprinting the pattern onto the substrate.
[0004] In the lithographic apparatus, many moving parts may be
provided. Movements may for example be performed by a substrate
stage, a patterning device stage (e.g. a mask stage), cooling
devices, etc. These movements may result in vibrations or other
disturbances which may act on a projection system of the
lithographic apparatus (also referred to as projection lens or
lens). Thereby, vibrations or other disturbances of the projection
system as a whole, and/or of optical elements thereof, may occur.
Previously, an active lens mount has been devised in order to
reduce an effect of such vibrations. In such active lens mount, a
first piezo element is provided to exert a force on the projection
system, and a second piezo element to measure the force. Using a
suitable control system, a resulting force on the projection system
may be reduced.
SUMMARY
[0005] It is desirable to provide an improved active mount.
[0006] According to an embodiment of the invention, there is
provided a mount to hold an object, including: a first
piezoelectric element to exert a force on the object, a second
piezoelectric element to measure the force, and an interconnection
member interposed between the first and second piezoelectric
elements, the interconnection member including a cut.
[0007] In another embodiment of the invention, there is provided a
lithographic apparatus including: an illumination system configured
to condition a radiation beam; a support constructed to support a
patterning device, the patterning device being capable of imparting
the radiation beam with a pattern in its cross-section to form a
patterned radiation beam; a substrate table constructed to hold a
substrate; and a projection system configured to project the
patterned radiation beam onto a target portion of the substrate,
the projection system being mounted to a reference structure of the
lithographic apparatus by a mount of the lithographic apparatus,
the mount including: a first piezoelectric element to exert a force
on the projection system, a second piezoelectric element to measure
the force, and an interconnection member interposed between the
first and second piezoelectric elements, the interconnection member
including a cut.
[0008] In an further embodiment of the invention, there is provided
a method for tuning a mount, the mount to hold an object and
including: a first piezoelectric element to exert a force on the
object, a second piezoelectric element to measure the force, and an
interconnection member interposed between the first and second
piezoelectric elements, the method including repeating (a)
measuring a remaining cross talk of the mount, and (b) cutting into
the interconnection member, until the remaining crosstalk reaches a
predetermined level.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Embodiments of the invention will now be described, by way
of example only, with reference to the accompanying schematic
drawings in which corresponding reference symbols indicate
corresponding parts, and in which:
[0010] FIG. 1 depicts a lithographic apparatus in which an
embodiment of the invention may be employed;
[0011] FIG. 2 depicts a piezo active lens mount as presently
applied in a lithographic apparatus according to an embodiment of
the invention;
[0012] FIG. 3 depicts a piezo stack of such piezo active mount
according to an embodiment of the invention;
[0013] FIG. 4 depicts a frequency response of such piezo stack;
[0014] FIG. 5A-E depict a piezo stack of an active lens mount
according to embodiments of the invention; and
DETAILED DESCRIPTION
[0015] FIG. 1 schematically depicts a lithographic apparatus
according to one embodiment of the invention. The apparatus
includes an illumination system (illuminator) IL configured to
condition a radiation beam B (e.g. UV radiation or any other
suitable radiation), a patterning device support or mask support
structure (e.g. a mask table) MT constructed to support a
patterning device (e.g. a mask) MA and connected to a first
positioning device PM configured to accurately position the
patterning device in accordance with certain parameters. The
apparatus also includes a substrate table (e.g. a wafer table) WT
or "substrate support" constructed to hold a substrate (e.g. a
resist-coated wafer) W and connected to a second positioning device
PW configured to accurately position the substrate in accordance
with certain parameters. The apparatus further includes a
projection system (e.g. a refractive projection lens system) PS
configured to project a pattern imparted to the radiation beam B by
patterning device MA onto a target portion C (e.g. including one or
more dies) of the substrate W.
[0016] The illumination system may include various types of optical
components, such as refractive, reflective, magnetic,
electromagnetic, electrostatic or other types of optical
components, or any combination thereof, to direct, shape, or
control radiation.
[0017] The patterning device support holds the patterning device in
a manner that depends on the orientation of the patterning device,
the design of the lithographic apparatus, and other conditions,
such as for example whether or not the patterning device is held in
a vacuum environment. The patterning device support can use
mechanical, vacuum, electrostatic or other clamping techniques to
hold the patterning device. The patterning device support may be a
frame or a table, for example, which may be fixed or movable as
required. The patterning device support may ensure that the
patterning device is at a desired position, for example with
respect to the projection system. Any use of the terms "reticle" or
"mask" herein may be considered synonymous with the more general
term "patterning device."
[0018] The term "patterning device" used herein should be broadly
interpreted as referring to any device that can be used to impart a
radiation beam with a pattern in its cross-section so as to create
a pattern in a target portion of the substrate. It should be noted
that the pattern imparted to the radiation beam may not exactly
correspond to the desired pattern in the target portion of the
substrate, for example if the pattern includes phase-shifting
features or so called assist features. Generally, the pattern
imparted to the radiation beam will correspond to a particular
functional layer in a device being created in the target portion,
such as an integrated circuit.
[0019] The patterning device may be transmissive or reflective.
Examples of patterning devices include masks, programmable mirror
arrays, and programmable LCD panels. Masks are well known in
lithography, and include mask types such as binary, alternating
phase-shift, and attenuated phase-shift, as well as various hybrid
mask types. An example of a programmable mirror array employs a
matrix arrangement of small mirrors, each of which can be
individually tilted so as to reflect an incoming radiation beam in
different directions. The tilted mirrors impart a pattern in a
radiation beam which is reflected by the mirror matrix.
[0020] The term "projection system" used herein should be broadly
interpreted as encompassing any type of projection system,
including refractive, reflective, catadioptric, magnetic,
electromagnetic and electrostatic optical systems, or any
combination thereof, as appropriate for the exposure radiation
being used, or for other factors such as the use of an immersion
liquid or the use of a vacuum. Any use of the term "projection
lens" herein may be considered as synonymous with the more general
term "projection system".
[0021] As here depicted, the apparatus is of a transmissive type
(e.g. employing a transmissive mask). Alternatively, the apparatus
may be of a reflective type (e.g. employing a programmable mirror
array of a type as referred to above, or employing a reflective
mask).
[0022] The lithographic apparatus may be of a type having two (dual
stage) or more substrate tables or "substrate supports" (and/or two
or more mask tables or "mask supports"). In such "multiple stage"
machines the additional tables or supports may be used in parallel,
or preparatory steps may be carried out on one or more tables or
supports while one or more other tables or supports are being used
for exposure.
[0023] The lithographic apparatus may also be of a type wherein at
least a portion of the substrate may be covered by a liquid having
a relatively high refractive index, e.g. water, so as to fill a
space between the projection system and the substrate. An immersion
liquid may also be applied to other spaces in the lithographic
apparatus, for example, between the patterning device (e.g. mask)
and the projection system Immersion techniques can be used to
increase the numerical aperture of projection systems. The term
"immersion" as used herein does not mean that a structure, such as
a substrate, must be submerged in liquid, but rather only means
that a liquid is located between the projection system and the
substrate during exposure.
[0024] Referring to FIG. 1, the illuminator IL receives a radiation
beam from a radiation source SO. The source and the lithographic
apparatus may be separate entities, for example when the source is
an excimer laser. In such cases, the source is not considered to
form part of the lithographic apparatus and the radiation beam is
passed from the source SO to the illuminator IL with the aid of a
beam delivery system BD including, for example, suitable directing
mirrors and/or a beam expander. In other cases the source may be an
integral part of the lithographic apparatus, for example when the
source is a mercury lamp. The source SO and the illuminator IL,
together with the beam delivery system BD if required, may be
referred to as a radiation system.
[0025] The illuminator IL may include an adjuster AD configured to
adjust the angular intensity distribution of the radiation beam.
Generally, at least the outer and/or inner radial extent (commonly
referred to as a-outer and a-inner, respectively) of the intensity
distribution in a pupil plane of the illuminator can be adjusted.
In addition, the illuminator IL may include various other
components, such as an integrator IN and a condenser CO. The
illuminator may be used to condition the radiation beam, to have a
desired uniformity and intensity distribution in its
cross-section.
[0026] The radiation beam B is incident on the patterning device
(e.g., mask) MA, which is held on the patterning device support
(e.g., mask table) MT, and is patterned by the patterning device.
Having traversed the patterning device (e.g. mask) MA, the
radiation beam B passes through the projection system PS, which
focuses the beam onto a target portion C of the substrate W. With
the aid of the second positioning device PW and position sensor IF
(e.g. an interferometric device, linear encoder or capacitive
sensor), the substrate table WT can be moved accurately, e.g. so as
to position different target portions C in the path of the
radiation beam B. Similarly, the first positioning device PM and
another position sensor (which is not explicitly depicted in FIG.
1) can be used to accurately position the patterning device (e.g.
mask) MA with respect to the path of the radiation beam B, e.g.
after mechanical retrieval from a mask library, or during a scan.
In general, movement of the patterning device support (e.g. mask
table) MT may be realized with the aid of a long-stroke module
(coarse positioning) and a short-stroke module (fine positioning),
which form part of the first positioning device PM. Similarly,
movement of the substrate table WT or "substrate support" may be
realized using a long-stroke module and a short-stroke module,
which form part of the second positioner PW. In the case of a
stepper (as opposed to a scanner) the patterning device support
(e.g. mask table) MT may be connected to a short-stroke actuator
only, or may be fixed. Patterning device (e.g. mask) MA and
substrate W may be aligned using patterning device alignment marks
M1, M2 and substrate alignment marks P1, P2. Although the substrate
alignment marks as illustrated occupy dedicated target portions,
they may be located in spaces between target portions (these are
known as scribe-lane alignment marks). Similarly, in situations in
which more than one die is provided on the patterning device (e.g.
mask) MA, the patterning device alignment marks may be located
between the dies.
[0027] The depicted apparatus could be used in at least one of the
following modes:
1. In step mode, the patterning device support (e.g. mask table) MT
or "mask support" and the substrate table WT or "substrate support"
are kept essentially stationary, while an entire pattern imparted
to the radiation beam is projected onto a target portion C at one
time (i.e. a single static exposure). The substrate table WT or
"substrate support" is then shifted in the X and/or Y direction so
that a different target portion C can be exposed. In step mode, the
maximum size of the exposure field limits the size of the target
portion C imaged in a single static exposure. 2. In scan mode, the
patterning device support (e.g. mask table) MT or "mask support"
and the substrate table WT or "substrate support" are scanned
synchronously while a pattern imparted to the radiation beam is
projected onto a target portion C (i.e. a single dynamic exposure).
The velocity and direction of the substrate table WT or "substrate
support" relative to the patterning device support (e.g. mask
table) MT or "mask support" may be determined by the
(de-)magnification and image reversal characteristics of the
projection system PS. In scan mode, the maximum size of the
exposure field limits the width (in the non-scanning direction) of
the target portion in a single dynamic exposure, whereas the length
of the scanning motion determines the height (in the scanning
direction) of the target portion. 3. In another mode, the
patterning device support (e.g. mask table) MT or "mask support" is
kept essentially stationary holding a programmable patterning
device, and the substrate table WT or "substrate support" is moved
or scanned while a pattern imparted to the radiation beam is
projected onto a target portion C. In this mode, generally a pulsed
radiation source is employed and the programmable patterning device
is updated as required after each movement of the substrate table
WT or "substrate support" or in between successive radiation pulses
during a scan. This mode of operation can be readily applied to
maskless lithography that utilizes programmable patterning device,
such as a programmable mirror array of a type as referred to
above.
[0028] Combinations and/or variations on the above described modes
of use or entirely different modes of use may also be employed.
[0029] An embodiment of an active lens mount is depicted in FIG. 2.
FIG. 2 depicts an active lens mount (also referred to as active
mount) having a top part with a top surface 27 and a bottom part
with a bottom surface 28. The top part and bottom part are
interconnected by resilient structures 50 at both sides.
Furthermore, the top part (identified by 25) and bottom part are
interconnected by piezoelectric actuator-sensor combinations,
identified in FIG. 2 as 30, 40. Each of the actuator-sensor
combinations includes a piezoelectric element acting as an actuator
and a piezoelectric element acting as a sensor. By driving the
actuator with a suitable electric signal, an expansion of the
piezoelectric actuator element may be achieved. A required force
acting via the piezoelectric elements 30, 40 between the top part
and the bottom part may be derived from a signal obtained from the
piezoelectric sensor 40. A suitable control system (broadly termed
"controller") may be provided to drive each of the actuators 30,
thereby taking into account a respective signal obtained from the
corresponding sensor 40, so as to counteract vibrations,
disturbances etc. having an effect on the top part 25. In an
embodiment, 3 of such depicted active lens mounts may be used. The
projection system PS (as depicted in FIG. 1) may hence be mounted
on 3 lens mounts as depicted. As each lens mount enables to
generate forces in two directions (in this example for example the
directions 70 and 81 as indicated in FIG. 2), a correction in
multiple degrees of freedom, preferably in 6 degrees of freedom,
may be provided thereby. It is noted that FIG. 2 further depicts
attachment holes 90 provided in the top part and bottom part so as
to enable the active lens mount to be adequately fastened.
Furthermore, a compression bolt 60 may be provided to press the top
and bottom surfaces 27, 28 together. Such compression bolt may
however in other embodiments be omitted, as a compression force may
already be provide by the weight of the projection system
itself.
[0030] A more detailed, however still schematic view of an
embodiment of the piezo actuator-sensor combination is depicted in
FIG. 3. In this embodiment, a stack is provided including the
piezoelectric sensor 30, the piezoelectric actuator 40, and an
interconnection member 20 to interconnect the actuator 30 and
sensor 40. Respective mounts, with which the sensor actuator
assembly is connected to the bottom and top part are referred to in
FIG. 3 by reference numeral 10. The identified items are
interconnected by gluing, respective glue layers being
schematically indicated in FIG. 3 and indentified by reference
numeral 70.
[0031] A piezoelectric actuator includes a crystal structure which,
when applying an electrical voltage to it, will result in a force
in the direction F as referred to in FIG. 3 (whether the force in
the direction as depicted is positive or negative depends on a
polarity of the applied voltage, as, depending on the polarity of
the applied voltage, the piezo material will exhibit a tendency to
expand or a tendency to contract) which may result in an expansion
or contraction, and a corresponding increase/decrease of the
dimension of the actuator 30 in this direction. When deforming
however, the piezoelectric element does not only increase or
decrease its dimension along the direction F, however also a
deformation along a width of the actuator may occur. This
deformation will, via the glue 70, result in a deformation of the
interconnection member 20. Ideally, the sensor 40 would only sense
forces acting on the assembly of actuator 30, sensor 40 and
interconnection member 20 along the direction F, however the
deformation of the actuator 30, and consequential deformation of
the interconnection member 20, will result in a deformation of a
contacting surface where the interconnection member 20 contacts,
via the glue layer 70, the sensor 40. As a consequence, a signal
will be generated by the sensor 40 in response to such
deformations, hence resulting in a crosstalk. This behavior results
in a frequency response of the sensor 40 as depicted FIG. 4
(continuous lines, the dashed lines will be referred to later).
Along a horizontal axis of FIG. 4, a frequency scale is provided.
Along a vertical axis, in the upper part, a magnitude of the
transfer is provided, while along the vertical axis, in the lower
part, the phase PH of the transfer is depicted. As can be seen, for
relatively high frequencies, in this example above 100 Hz, the
projection system will remain quasi stationary, and therefore a
drive of the actuator will linearly result in a measurement by the
sensor. In an ideal case, for very low frequencies, approaching
zero, the magnitude of the transfer would ideally be zero, as a
constant drive of the actuator will result in a displacement of the
projection system, which will, after the displacement has settled,
provide a substantially zero output at the sensor. Hence, in the
stationary case, a transfer of zero would ideally be expected,
which results in an ideal transfer frequency characteristic
substantially in a quadratic relation with a frequency in a certain
frequency range. At low frequencies however, another effect may
play an important role, namely the deformation described with
reference to FIG. 3. This deformation will, at low frequencies,
result in a transfer because of the above described crosstalk that
takes place as a result of the deformation of the interconnection
member 20. As a result, a frequency characteristic as depicted in
FIG. 4 is obtained, having a flat response for low frequencies,
followed by a response quadratically depending on the frequency,
again followed by a flat response for higher frequencies.
[0032] In an embodiment, the interconnection member may be provided
with a cut C which may reduce a crosstalk from the actuator 30 to
the sensor 40. A variety of embodiments of such cut will be
described with reference to FIG. 5A -5E. In general, the cut may
assist to reduce a crosstalk, as a resulting deformation of the
interconnection member 20 at its side facing the sensor 40, the
deformation as a result of the actuation and deformation of the
actuator 30. Generally, the cut aims at maintaining a high
stiffness in the direction of the force F, while reducing or better
dividing a deformation of the face of the interconnection member
which is glued to the sensor. In an embodiment, a reduction of the
crosstalk may be obtained in two ways: firstly, a deformation of
the surface to which the sensor is connected, may be reduced.
Secondly, a reduction in crosstalk also occurs when positive and
negative effects of deformation substantially compensate each
other. As an example, a compression of the piezo electric sensor 40
in vertical direction and an expansion thereof in the same
direction results in opposite electrical charges. In case, as a
result of deformation, a part of the sensor is compressed while
another part of the sensor is extended in the same direction,
resulting positive and negative charges may at least partly
compensate each other, thereby reducing an output of the sensor as
a result of such deformation. Making use of one or both of these
effects, a plurality of embodiments have been devised, which will
be described below with reference to FIGS. 5A-5E. In FIG. 5A, the
interconnection member has been provided with a lateral cut in a
plane substantially perpendicular to a direction of the force.
Thereby, a stiffness in the direction of the force (in FIGS. 5A-E
the vertical direction) is maintained, while a deformation may be
reduced. In this embodiment, lateral cuts are provided at the
opposite side of the interconnection member, thereby providing a
degree of symmetry, which enables to improve cancelling a positive
and negative charges which are due to extraction and contraction of
parts of the piezo electric sensor. It has been devised that a
depth of the cuts is beneficially set in a range so as to leave a
remaining part of the interconnection member between the cuts to
have a width in a range from 40% to 80% of the total width of the
interconnection member.
[0033] Another example is schematically depicted in FIG. 5B. Here,
the interconnection member is provided with a triangular cut. The
same remarks as made further to the FIG. 5A embodiment also apply
here. Comparing the embodiments in accordance with FIGS. 5A and 5B,
a similar stiffness in the direction of the force may be observed,
however differences in their deformation behavior may be observed:
In the embodiment in accordance with FIG. 5A, an upper and lower
part of the interconnection member (i.e. on both sides of the cut)
may exhibit a higher bending stiffness and exhibit a different
behavior in transverse contraction.
[0034] A still further embodiment is shown in FIG. 5C, where the
cut extends along the direction of the force i.e. in FIG. 5C in
vertical direction, thereby in this example not only dividing the
interconnection member in parts, but also the first and second
piezoelectric elements. Alternatively, the cut may extend only
through the interconnection member, thereby leaving the
piezoelectric elements each as an integral part. As a result,
smaller interconnection members and smaller piezoelectric elements
are provided, thereby resulting in a lower deformation effect. In
an embodiment, the interconnection member as well as the first and
second piezoelectric elements are divided in 4 parts, the cuts
hence being provided in planes substantially perpendicular to each
other.
[0035] In a still further embodiment, a plurality of parallel cuts
is provided. Thereby, similarly to the other embodiments, a
stiffness in the direction of the force may be maintained, while
crosstalk may be reduced. The parallel cuts may be provided along
to planes, the planes preferably being substantially perpendicular
to each other, so as to form a structure of poles in an
intermediate part of the interconnection member. A variant to the
embodiment depicted in FIG. 5D is depicted in FIG. 5E. Here, double
cuts are provided thereby leaving an interconnection plate IP
between the poles.
[0036] Benefits of the interconnection member having a cut may in
general be that a crosstalk between the first piezoelectric element
(i.e. the piezoelectric actuator) and the second piezoelectric
element (i.e. the piezoelectric sensor) is reduced. Specific
benefits may be achieved with the various embodiments in accordance
with FIGS. 5A-5E. The various embodiments may exhibit differences
in bending stiffness, lateral stiffness and stiffness in the
direction of the force (i.e. the actuation direction of the first
piezoelectric element). Differences between the embodiments
according to FIGS. 5A and 5B have been described above. In the
embodiment in accordance with FIG. 5C, a width-height ratio of the
interconnection member is changed, whereby stiffness may be
maintained at a same level. This may provide benefit in
circumstances where a low height of the interconnection member is
to be achieved. The embodiment in accordance with FIG. 5D may
provide for an interconnection member having a relatively low
stiffness in lateral direction (i.e. in a direction substantially
perpendicular to the direction of the force: in such a
configuration, when a length/width ratio of the remaining "poles"
would be to high and risk bending, the embodiment in accordance
with FIG. 5E would increase/reduce such a bending risk). Hence, the
difference embodiments may be applied to tailor a behavior of the
interconnection member to a specific need.
[0037] In an embodiment, the crosstalk may be dimensioned so as to
reach a certain level which is substantially opposite to a
crosstalk provided via the resilience 50 depicted in FIG. 2. As a
result, crosstalk obtained via the interconnection member and
crosstalk obtained via the parallel resilience 50 of the active
lens mount, may be substantially opposite, which may result in a
substantial reduction of an overall crosstalk, hence in an improved
effectiveness of the active lens mount.
[0038] In a further embodiment, a deformation member may be
provided in the interconnection member, the deformation member may
be formed, for example, by a piezoelectric actuator. Thereby, an
active fine tuning may be provided as a remaining crosstalk may be
reduced by a suitable deformation of interconnection member.
Furthermore, an actuator, such as a piezoelectric actuator may be
provided to act on the parallel resilience 50, thereby amending a
stiffness thereof to certain degree. As a result, a fine tuning may
be obtained as a stiffness of the parallel resilience, and hence a
crosstalk via the parallel resilience between the first and second
piezoelectric element, may be adjusted to be substantially equal
but opposite to the crosstalk via the deformation of the
interconnection member, thereby substantially reducing an overall
crosstalk.
[0039] As a result of the various embodiments of the invention, a
crosstalk of the interconnection member may be reduced, which may
as an example result in a change in the frequency characteristic in
accordance with the dashed lines depicted in FIG. 4, whereby for
lower frequencies, the quadratic relation with frequency remains,
as indicated by the dashed lines.
[0040] In each of the above embodiments, a tuning may be obtained
by assembling an active lens mount of a lithographic apparatus,
measuring a crosstalk of the active lens mount, the crosstalk
between the first piezoelectric element and the second
piezoelectric element, and cutting into the interconnection member
(e.g. in accordance with any of the embodiments depicted and
described with reference to FIGS. 5A-5E), until the crosstalk
reaches a predetermined level. Thereby, an adjustment may be made
to take account of a variety of factors that could have an effect
on the remaining crosstalk, such as manufacturing tolerances,
differences in weight of the projection system, and other factors.
A similar iterative improvement may also be performed in a finite
element computer simulation without actually manufacturing or
mechanically processing a series of active lens mounts. The above
described concept may not only be applied for an active lens mount
of a lithographic apparatus. It will be understood that the same
concept may be applied to any application hence may be applied to
any active mount.
[0041] Although in the above, reference has been made to
application is a lithographic apparatus, it will be understood that
the piezoelectric active mount may be applied for many other
applications, some examples of which being provided below: The
piezoelectric active mount in accordance with the invention may for
example be applied in:
[0042] a vibration damper of a turning machine, a polishing
mashing, a cutter machine, a lapping machine, etc for accurate
manufacturing of parts, such as mechanical parts of optical parts.
Therefore, the mount may be applied to mount such a machine and/or
the to be machined product.
[0043] a vibration damper of an optical target which is located in
an imaging plane, focal plane etc. of a projection system. Examples
may include a substrate or substrate table in a lithographic
apparatus, scanning electron microscope etc.
[0044] a vibration damper of a dish antenna telescope etc.
[0045] in applications where parts are to be accurately aligned is
respect of each other, an application thereof may for example be
found in a particle accelerator.
[0046] The above examples should not be considered limitative.
Rather, the mount as described in this document may be applied in
any vibration damping application.
[0047] Although specific reference may be made in this text to the
use of lithographic apparatus in the manufacture of ICs, it should
be understood that the lithographic apparatus described herein may
have other applications, such as the manufacture of integrated
optical systems, guidance and detection patterns for magnetic
domain memories, flat-panel displays, liquid-crystal displays
(LCDs), thin-film magnetic heads, etc. The skilled artisan will
appreciate that, in the context of such alternative applications,
any use of the terms "wafer" or "die" herein may be considered as
synonymous with the more general terms "substrate" or "target
portion", respectively. The substrate referred to herein may be
processed, before or after exposure, in for example a track (a tool
that typically applies a layer of resist to a substrate and
develops the exposed resist), a metrology tool and/or an inspection
tool. Where applicable, the disclosure herein may be applied to
such and other substrate processing tools. Further, the substrate
may be processed more than once, for example in order to create a
multi-layer IC, so that the term substrate used herein may also
refer to a substrate that already contains multiple processed
layers.
[0048] Although specific reference may have been made above to the
use of embodiments of the invention in the context of optical
lithography, it will be appreciated that the invention may be used
in other applications, for example imprint lithography, and where
the context allows, is not limited to optical lithography. In
imprint lithography a topography in a patterning device defines the
pattern created on a substrate. The topography of the patterning
device may be pressed into a layer of resist supplied to the
substrate whereupon the resist is cured by applying electromagnetic
radiation, heat, pressure or a combination thereof. The patterning
device is moved out of the resist leaving a pattern in it after the
resist is cured.
[0049] The terms "radiation" and "beam" used herein encompass all
types of electromagnetic radiation, including ultraviolet (UV)
radiation (e.g. having a wavelength of or about 365, 248, 193, 157
or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a
wavelength in the range of 5-20 nm), as well as particle beams,
such as ion beams or electron beams.
[0050] The term "lens", where the context allows, may refer to any
one or combination of various types of optical components,
including refractive, reflective, magnetic, electromagnetic and
electrostatic optical components.
[0051] While specific embodiments of the invention have been
described above, it will be appreciated that the invention may be
practiced otherwise than as described. For example, the invention
may take the form of a computer program containing one or more
sequences of machine-readable instructions describing a method as
disclosed above, or a data storage medium (e.g. semiconductor
memory, magnetic or optical disk) having such a computer program
stored therein.
[0052] The descriptions above are intended to be illustrative, not
limiting. Thus, it will be apparent to one skilled in the art that
modifications may be made to the invention as described without
departing from the scope of the claims set out below.
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